Presently existing meter reading systems typically utilize a central poling computer complex. The central complex communicates with remote meters through power lines, existing telephone systems or some other electromagnetic communications link. Examples of metering systems utilizing a power line as the communications link are described in U.S. Pat. Nos. 4,012,734 (Jagoda et al, 1977), 3,973,240 (Fong, 1976), 3,914,757 (Finlay, Jr., 1975), 3,445,814 (Spalti, 1969), and 3,258,692 (Jacomini et al, 1966). Similarly, examples of unit metering systems wherein the communications link is provided through an existing telephone system are described in U.S. Pat. Nos. 3,829,835 (Stewart, Jr., 1974), 3,820,073 (Vercellotti et al, 1974), 3,503,61 (Bray et al, 1970), 3,492,649 (Polillo, 1970), 3,478,342 (Alldritt et al, 1969), 3,414,676 (Long, 1968) and 4,008,458 (Wensley, 1977).
U.S. Pat. Nos. 3,510,841 (Lejon, 1970), 3,750,156 (Martell, 1973), and 4,006,461 (Coulter, 1977) describe remote metering systems using other electromagnetic communication links.
In all cases, however, the central complex initiates the meter reading functions by interrogating a transponder at the meter location. The transponder transmits accumulated data back to the central complex in response to the interrogation.
The prior art transponder systems, however, are unduly complex and expensive. For example, where the communications link is effected through power lines, provisions for balancing the power lines must be made. Similarly, where an existing telephone system is used as the communications link, the telephone exchange must be modified to directly access the transponder. Absent modification, the interrogation of the remote meter causes other telephones located in the users home to ring. In addition, the central poling computer must store the account numbers of the respective users and relate the account numbers to the users telephone numbers.
Sensor monitoring systems which initiate a telephone call to a central complex upon sensing of predetermined alarm conditions are also known. An example of such a system is described in U.S. Pat. No. 3,842,208 issued Oct. 15, 1974 to Theodoros G. Paraskevakos. This system may be applied to metering applications, initiating a report, or upon sensing consumption of a predetermined metered quantity. This type of reporting lacks predictability and thus is not readily suitable for a practicable billing system.